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The Work of Titin Protein Folding as a Major Driver in Muscle Contraction
Annual Review of Physiology ( IF 15.7 ) Pub Date : 2018-02-12 00:00:00 , DOI: 10.1146/annurev-physiol-021317-121254
Edward C. Eckels 1, 2 , Rafael Tapia-Rojo 1 , Jamie Andrés Rivas-Pardo 1 , Julio M. Fernández 1
Affiliation  

Single-molecule atomic force microscopy and magnetic tweezers experiments have demonstrated that titin immunoglobulin (Ig) domains are capable of folding against a pulling force, generating mechanical work that exceeds that produced by a myosin motor. We hypothesize that upon muscle activation, formation of actomyosin cross bridges reduces the force on titin, causing entropic recoil of the titin polymer and triggering the folding of the titin Ig domains. In the physiological force range of 4–15 pN under which titin operates in muscle, the folding contraction of a single Ig domain can generate 200% of the work of entropic recoil and occurs at forces that exceed the maximum stalling force of single myosin motors. Thus, titin operates like a mechanical battery, storing elastic energy efficiently by unfolding Ig domains and delivering the charge back by folding when the motors are activated during a contraction. We advance the hypothesis that titin folding and myosin activation act as inextricable partners during muscle contraction.

中文翻译:


Titin蛋白折叠作为肌肉收缩的主要驱动力

单分子原子力显微镜和磁性镊子实验已经证明,肌动蛋白免疫球蛋白(Ig)结构域能够抵抗拉力折叠,产生的机械功超过肌球蛋白电机产生的功。我们假设在肌肉激活后,放线菌素跨桥的形成降低了对肌动蛋白的作用力,导致肌动蛋白聚合物的熵回缩并触发了肌动蛋白Ig结构域的折叠。在肌肉力作用于4-15牛顿的生理力范围内,单个Ig结构域的折叠收缩可产生200%的熵回弹功,并且发生的力超过单个肌球蛋白马达的最大失速力。因此,替丁的运作方式就像机械电池一样,当电机在收缩过程中启动时,通过展开Ig域有效地存储弹性能并通过折叠将电荷传递回去。我们提出了这样的假说:在肌肉收缩过程中,titin折叠和肌球蛋白激活是不可分割的伴侣。

更新日期:2018-02-12
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